Question

my son has a 2000 hyundy sonata, two weeks ago the breake lock and they started to burn the pads, i change the front rotors and breake pads, but after all that work the car droved ok for about 5 miles and the breakes locked again,and started to burn the pads again. some one told me to replace the vacum cilynder behind the master cylinder I did that and I stil have the same problem. the vacum cylinder does not return to its oroginal place, instead the cyclinder holds the air pressure and locks the bralkes, I have to unhook the vacum hose and release the air pressure before I can continue, please help I can affort to send the car to a profesional shop.

I suspect the valve in your power booster is malfunctioning. The booster is an empty shell that is divided into two chambers by a rubber diaphragm. There is a valve in the diaphragm that remains open while your foot is off the brake pedal so that vacuum is allowed to fill both chambers. When you step on the brake pedal, the valve in the diaphragm closes, separating the two chambers and another valve opens to allow air in the chamber on the brake pedal side. In your case the valve is not opening when you take your foot off the brake. I do not believe you can repair the valve. You need to replace the entire booster assembly.

ckeck your brake caliber hose if they are not letting the fluid return to the brake resivoir the hose are calapsing and holeing brakes but if this is going gone the hyundai will pull to one side or orther .